Given a list of ranges to stream, stream_transfer_task will create an
reader with the ranges and create a rpc stream connection on all the shards.
When user provides ranges to repair with -st -et options, e.g.,
using scylla-manger, such ranges can belong to only one shard, repair
will pass such ranges to streaming.
As a result, only one shard will have data to send while the rpc stream
connections are created on all the shards, which can cause the kernel
run out of ports in some systems.
To mitigate the problem, do not open the connection if the ranges do not
belong to the shard at all.
Refs: #4708
64a4c0ede2